Vascular dementia is caused by poor blood flow to the brain, depriving brain cells of the nutrients and oxygen they need to function normally. Vascular dementia can result from any number of conditions that narrow the blood vessels, including stroke, diabetes and hypertension. Vascular dementia has a sudden onset and a stepwise progression, typically with abrupt changes in cognitive ability. The cognitive profile of vascular dementia is highly variable depending on the location of the stroke. After a stroke, the risk of dementia doubles. Controlling hypertension, weight, diabetes and heart disease are vitally important to helping prevent vascular dementia.